I am not sure whether is it because I am breastfeeding, but my immunity was kinda of bad lately, such that I would sneeze whenever the wind from the fan blows at me. Yes, it was that bad. Baby was also sort of getting a bit phlegm and would be snoring slightly in his sleep. I am generally quite cautious when it comes to supplement and medication (don't give a shit when it comes to food...have been guilty of snacking).
Based on my research, it is okay to take Vit C supplements to boost your immunity even when you are breastfeeding. The brand that I am trying needs no introduction. Blackmores is quite reputable. I have tried their folic acid too (highly potent but the pills were so huge and it made me nauseous). Try and Review sent me the chewables Bio C for review and I found them to be rather delicious and effective.
Although the recommendation is to take 2 every meal, I personally feel that 2 a day should be more than suffice to see an effect for maintenance. I still think that the best form of nutrients definitely come through food and not supplements unless of couse you are lacking due to some reasons.